ES2755189T3 - Procedure to suppress the formation of 3,3,3-trifluoropropin in the manufacture of fluorocarbons - Google Patents

Abstract

A method of preventing the formation of 3,3,3-trifluoropropyne during the manufacture of fluorocarbon compounds, said method comprising the steps of: (a) forming a fluorocarbon compound in a reaction process that generates reaction products comprising one or more acids; (b) carrying out one or more bulk acid separation processes substantially free of caustics in the reaction products of step (a); and (c) carrying out one or more trace acid removal processes to remove the acids remaining after step (b), thereby preventing the formation of 3,3,3-trifluoropropyne; wherein the bulk removal of the acids in step (b) comprises treating the reaction products with a first scrubbing solution in a first absorber to remove most of the acid.

Description

DESCRIPTION

Procedure to suppress the formation of 3,3,3-trifluoropropin in the manufacture of fluorocarbons

FIELD OF THE INVENTION

This invention relates to a process for the suppression of 3,3,3-trifluoropropin during the manufacture of fluorocarbons, including fluoro-olefins and hydrochloro-fluoro-olefins. More particularly, this invention is directed to a process for suppressing 3,3,3-trifluoropropin formation during the processes for the manufacture of HCFO-1233zd (E), HCFO-1233zd (Z), HFO-1234ze (E) and / or HFO-1234ze (Z).

BACKGROUND OF THE INVENTION

This invention especially relates to improvements in the production of HCFO-1233zd (E), HCFO-1233zd (Z), HFO-1234ze (E), and HFO-1234ze (Z). As used herein, the designations 1233zd and 1234ze will be used when referring to the E or Z isomers, or a combination thereof.

These compounds have a zero or low ozone depletion potential, as well as a low global warming potential, so they are useful and desirable as substitutes for existing materials used in refrigeration, foam blowing, solvents, monomers and others. applications where other fluorocarbons are currently used.

Methods of producing 1233zd are known in the art. See, for example, US Patent Publications. No.s 2012-0172636; 2012-0271069; and 2012-0271070, which describe both 1233zd and 1234ze production procedures.

A preferred embodiment for the manufacture of 1233zd is as follows:

HCC-240fa 3HF ^ 1233zd 4HCl

which takes place in a liquid phase reaction in the absence of a catalyst with a large excess of HF.

Methods of producing 1234ze have also been described. See, for example, US Pat. Nos. 7,485,760 and 7,638,660, in which the manufacture of 1234ze is described as follows:

HFC-245fa ^ 1234ze HF

which takes place in the vapor phase in the presence of a dehydrofluorination catalyst.

In the above procedures to produce 1233zd and / or 1234ze, the crude product is usually a mixture of the two Z and E isomers (also known as the cis and trans isomers, respectively). Typical procedures employ one or more purification methods, such as distillation, extraction, decantation, and absorption, to purify and recover the desired fluoro-olefin product. Since the reaction products include HCl and HF acids depending on the procedure, there is a need to separate these acid components during the product purification and recovery process. Although the massive separation of the acids is carried out by means of one or more purification techniques, such as distillation, extraction and / or decantation; An additional unit operation that is often used for removal of residual acidity is absorption through strong caustic solutions, such as KOH, NaOH, or the like, at a pH of about 11 or higher.

Methods for producing 3,3,3-trifluoropropin are also known in the art. See, for example, US Pat. No. 7,964,759. This patent describes a method of producing 3,3,3-trifluoropropin by contacting (Z) -1-halogen-3,3,3-trifluoropropene with a high concentration of a strong organic or inorganic base (pH> 10 ). Both 1233zd and 1234ze are 1-halogen-3,3,3-trifluoropropenes; 1233zd is 1-chloro-3,3,3-trifluoropropene and 1234ze is 1-fluoro-3,3,3-trifluoropropene.

As noted above, 3,3,3-trifluoropropin can be formed when compounds such as 1233zd and 1234ze are allowed to react with strong bases. In processes in which the desired product is one of those listed above, trifluoropropin is usually considered an unwanted impurity due to possible toxicity and flammability problems and therefore this compound is preferably removed if formed. The need to separate trifluoropropin necessarily increases the capital investment, as well as the operating costs associated with the production of one or more of the above compounds. Therefore, it would be much more desirable not to form trifluoropropin in the first place. Therefore, there is a need for means by which trifluoropropin formation can be avoided.

This invention provides a solution to this problem.

SUMMARY OF THE INVENTION

As shown above, 3,3,3-trifluoropropin can be formed when the 1233zd and / or 1234ze crude products are allowed to react with a strong caustic solution. Since it is known that reaction with a strong base solution can promote the formation of trifluoropropin, a procedure that does allow such a reaction should eliminate or reduce the formation of trifluoropropin.

The method described here is different from traditional fluorocarbon / fluoro-olefin processes, in which unrecoverable amounts of HF and / or HCl in the crude product containing one or more of 245fa, 1234ze, 1233zd, or other intermediates in manufacturing of said compounds, they are typically treated with water to remove most of the acid, followed by the absorption of residual HF and / or HCl in a circulating caustic washing system (containing an aqueous solution of NaOH, KOH, etc.) and finally dry the deacidified crude product saturated with water with molecular sieves and / or concentrated sulfuric acid.

In one embodiment, the crude product containing unrecoverable amounts of HF (and / or very small amounts of HCl) is treated with water in a first pass HF absorber with single pass water (or weak circulating HF solution) to separate the Most Acid This stream would then be treated in a second absorber with one pass water to remove additional amounts of acid. The essentially acid-free stream that may contain trace amounts of HF would optionally be cooled to selectively condense water to reduce the amount of moisture, followed by drying / absorption of HF in a circulating H ² SO ⁴ absorption system. Concentrated sulfuric acid provides a very effective means of drying fluorocarbons / fluoro-olefins and, in addition, has a high affinity for HF. Furthermore, the sulfuric acid that is used for drying and traces absorption of HF can be regenerated by means known in the art and reused in the process.

In this embodiment, the need to use a caustic component scrubber is eliminated, thus reducing the cost associated with supplying caustic components for the process and removing depleted caustic components (an aqueous mixture of caustic salts plus halide). Furthermore, there is an advantage in avoiding costs, as the need for the prior art to separate trifluoropropin is eliminated.

In another embodiment, the crude product containing unrecoverable amounts of HF (and / or very small amounts of HCl) is treated with water in a first pass HF absorber with single pass water (or weak circulating HF solution) to separate the most of the acid This stream would be treated in a second absorber with weak caustic solution circulating between pH 7 and 10 (inclusive) to separate additional amounts of acid. The acid free stream would then optionally be cooled to selectively condense water to reduce the amount of moisture, followed by drying in a circulating H ² SO ⁴ absorption system. Concentrated sulfuric acid provides a very effective means of drying fluorocarbons / fluoro-olefins. Furthermore, the sulfuric acid used for drying can be regenerated by means known in the art and reused in the process. The separated (E) -1233zd and / or (E) -1234ze can be isomerized to form the corresponding Z isomer. For example, HCFO- (Z) -1233zd can be formed from HCFO- (E) -1233zd by methods described in US Pat. No. 20120271069; and HFO- (Z) -1234ze can be formed from a mixture of E and Z isomers as described in US Pat. 20100022809.

It should be appreciated by those with ordinary experience in the technique (s) referred to in the present invention that any of the features described herein with respect to any particular aspect and / or embodiment of the present invention may be combined with one or plus any of the other features of any other aspects and / or embodiments of the present invention described herein, with modifications as appropriate to ensure compatibility of the combinations.

It is to be understood that both the foregoing general description and the following detailed description are by way of example and explanatory and are not restrictive of the invention as claimed. Other embodiments will become apparent to those skilled in the art from consideration of the specification and practice of the invention described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Various non-limiting schemes are shown to illustrate the invention.

Figure 1 shows a general scheme in the vapor phase to recover a product without formation of trifluoropropin.

Figure 2 shows a liquid phase scheme for deacidification with water, followed by phase separation of the organic layer from the aqueous HF layer. The organic layer is then dried by passing it through a tower filled with a desiccant. The desiccant, when chosen correctly, separates out both moisture and trace amounts of HF that may remain in the organic layer.

Figure 3 shows a liquid phase scheme for deacidification with water, followed by phase separation of the organic layer from the aqueous HF layer. The organic layer is then contacted with concentrated sulfuric acid to absorb moisture and trace HF.

Figure 4 shows a liquid phase scheme for deacidification with water, followed by phase separation of the organic layer from the aqueous HF layer. The organic layer is then vaporized and contacted with concentrated sulfuric acid to absorb moisture and trace HF.

Figure 5 shows a procedure for the manufacture of 1233zd with one of the embodiments of the invention described herein.

DETAILED DESCRIPTION OF THE INVENTION

A description of an embodiment of the invention using a 1233zd continuous procedure follows as the example in the illustration with vapor phase deacidification. This embodiment is shown in Figure 5.

Step (1) - Produce 1233zd from 240fa and excess HF by reaction:

240fa 3HF -> 1233zd 4HCl

Step (2) - Recover HCl and recycle unreacted intermediates and starting materials, including 240fa and HF. Treat the crude 1233zd (in the vapor state) containing HF in a water absorber using multiple phases or multiple absorbers to separate most of 1HF. Optionally, cool the resulting steam stream so that some of the water condenses but the raw 1233zd does not condense. Step (3) - Feed the chilled crude 1233zd (in the vapor state) into a sulfuric component scrubber which is a circulating concentrated sulfuric acid solution to remove both water and any residual HF. The resulting stream that is essentially free of moisture, HF, and 3,3,3-trifluoropropin can be subjected to distillation steps to further purify 1233zd.

The above procedure can also be used in a process to produce 1234ze from 245fa without trifluoropropin formation.

Alternative Embodiments:

Referring to Figure 2, a liquid phase deacidification procedure may also be used, in which liquid crude may be contacted with water in batch mode or in continuous mode in single or multiple stages (Figure 1 shows a single stage). After each of the steps, the organic material would phase separate from the aqueous phase.

In another alternative embodiment, again referring to Figure 2, continuous extraction can be used in this step. The resulting crude material that is saturated with water and trace HF can be treated with a desiccant, such as silica gel, molecular sieves, or alumina, which is also effective in separating HF.

Referring to Figure 3, the crude liquid organic compound can be contacted with concentrated sulfuric acid followed by phase separation (or in an extraction column).

Referring to Figure 4, in yet another alternative method, the crude liquid organic compound may be vaporized first and fed to a circulating sulfuric compound scrubber as described in step 5 above. Example 1

1233zd is produced by the methods described in the specification of US Pat. No. 2012-0172636. The crude product contains a maximum of approximately 50 ppm of 3,3,3-trifluoropropin.

The crude product leaving the reactor is subjected to recovery of HCl and recovery HF to recover a stream with the following composition:

The temperature of the feed stream is approximately 46 ° C and the pressure is approximately 10 psig (0.69 bar).

The overhead stream is fed to an HF absorber that has a continuous single pass fresh water feed supply at room temperature (approximately 25 ° to 30 ° C). The HF absorber is packed with random packing and has enough theoretical stages to absorb at least 99% of the incoming HF. The amount of water is adjusted to produce a nominal 5% aqueous HF solution, as well as provide sufficient moisture to the packaging. The stream leaving the HF absorber, which is saturated with water, is cooled in order to condense part of the water. The resulting stream is continuously fed to a sulfuric acid drier to separate the remaining moisture and trace HF. The sulfuric acid dryer consists of a pump reservoir that is initially filled with 99 + wt% H ² SO ⁴ connected to a packing tower. A pump is used to circulate H ² SO ⁴ from the pump reservoir to the top of the packing tower, while the process stream flows upward.

The stream leaving the top of the sulfuric acid dryer is analyzed and found to contain no additional 3,3,3-trifluoropropin.

Example 2

1233zd (E) 99.9% pure was passed through a scrubber (wash column dimensions: 6 inches (15.24 cm) in diameter, 10 feet tall (305 cm)) in which a Diluted NaOH solution at pH 10. The feed rate of 1233zd (E) was maintained at 1-2 lb / h (0.45 - 0.90 kg / h). The product leaving the scrubber was passed through a Drierite dryer (CaSO ⁴ ) and a sample was taken. 3,3,3-Trifluoropropin was not observed in the collected samples.

Example 3

Example 2 was repeated, except that the pH of the circulating solution was approximately 8. Again, as in Example 2, 3,3,3-trifluoropropin was not observed in the samples collected after the washer and dryer.

Example 4

A crude 1233zd stream consisting mainly of 1233zd (Z), 1233zd (E), unreacted HF, and HCl leaving a non-catalytic liquid phase fluorination reactor is fed to a distillation column. The purpose of the distillation column is to separate 1233zd (Z) prior to separation of HCl and HF from 1233zd (E) using a conventional caustic scrubbing system. The distillate stream from the top of the column contains HCl, HF, and 1233zd (E), low-boiling by-products, but not 1233zd (Z). A GC analysis of the distillate stream shows the presence of 10 ppm of 3,3,3-trifluoropropin.

The distillate stream is then fed in the form of a gas to the bottom of a continuous scrubbing system in which a 4% NaOH solution circulates through a packing column. The 4% NaOH effectively neutralizes all the HF and HCl in the stream and the 1233zd (E) exits from the top of the column. The stream is analyzed by GC and is found to still contain 10 ppm of 3,3,3-trifluoropropin.

A stream of mainly 1233zd (Z) is drawn from the bottom of the distillation column and collected for future use.

Comparative Example 1

1233zd is produced through the methods described in the specification of the US patent publication. No. 2012-0172636. The crude product contains a maximum of approximately 50 ppm of 3,3,3-trifluoropropin.

The raw product leaving the reactor had the following composition:

The organic composition in the above is the same as in Example 1. What differs is the amount of HF and HCl, because the reaction product was not subjected to recovery of HF and HCl. The weight percentage of the composition of the stream leaving the reactor represented in the previous Table is based on approximately 4.4 moles of organic compounds (average molecular weight of about 140 g / mol), about 18.5 moles of HCl and approximately 20 moles of HF.

The stream leaving the reactor was passed through a washing column of continuous caustic components. A 10% KOH solution was continuously circulated through the column at approximately 50 ° to 65 ° C to remove excess HF and HCl by-product. The acid free crude product exiting the wash column was then dried using Drierite (CaSO4). The crude product exiting the dryer was analyzed and the concentration of 3,3,3-trifluoropropin was found to be from 0.4% by weight to 0.7% by weight.

Comparative Example 2

1233zd is produced through the methods described in the specification of the US patent publication. No. 2012-0172636. The crude product contains a maximum of approximately 50 ppm of 3,3,3 trifluoropropin.

The crude product leaving the reactor is subjected to recovery of HCl and HF to recover a stream with the following composition:

The temperature of the feed stream is approximately 46 ° C and the pressure is approximately 10 psig (0.69 bar).

The above stream is fed to a circulating caustic scrubber having an initial concentration of 4% NaOH by weight. The stream leaving the circulating caustic component scrubber, which is saturated with water, is cooled in order to condense some of the water. The resulting stream is continuously fed to a sulfuric acid drier to remove remaining moisture. The sulfuric acid dryer consists of a pump reservoir that is initially filled with 99 + wt% H ² SO ⁴ connected to a packing tower. A pump is used to circulate H ² SO ⁴ from the pump reservoir to the top of the packing tower, while the process stream flows upward. The stream leaving the top of the sulfuric acid dryer is analyzed and found to contain approximately 800 to 2000 ppm of 3,3,3-trifluoropropin.

As used herein, the singular forms "a", "an" and "the", "the" include the plural, unless the context clearly dictates otherwise. Furthermore, when a quantity, concentration, or other value or parameter is given as a range, preferred range, or a list of upper preferable values and lower preferable values, it should be understood that it specifically describes all ranges formed from any pair of any limit of upper range or preferred value and any lower range limits or preferred value, regardless of whether the ranges are described separately. When a range of numerical values is mentioned in this specification, unless otherwise indicated, the range is intended to include their endpoints, and all integers and fractions within the range. The scope of the invention is not intended to be limited to the specific values mentioned when defining a range.

It should be understood that the above description is only illustrative of the present invention. Those skilled in the art can design various alternatives and modifications without departing from the invention. Accordingly, the present invention is intended to encompass all of these alternatives, modifications and variations that fall within the scope of the appended claims.

Claims (9)

1. A method to prevent the formation of 3,3,3-trifluoropropin during the manufacture of fluorocarbon compounds, said method comprising the steps of: (a) forming a fluorocarbon compound in a reaction process that generates reaction products comprising one or more acids; (b) carrying out one or more bulk acid separation processes substantially free of caustic components in the reaction products of step (a); and (c) carrying out one or more trace acid separation processes to separate the acids remaining after step (b), thereby avoiding the formation of 3,3,3-trifluoropropin; wherein the bulk removal of the acids in step (b) comprises treating the reaction products with a first scrubber solution in a first absorber to remove most of the acid. 2. The method of claim 1, wherein the fluorocarbon compound is selected from the group consisting of including fluorocarbons, fluoro-olefins and hydrochloro-fluoro-olefins. 3. The method of claim 2, wherein the fluorocarbon compounds include one or more of HCFO-1233zd (E), HCFO-1233zd (Z), HFO-1234ze (E) and HFO-1234ze (Z). 4. The method of claim 1, wherein the first purifying solution comprises water. 5. The method of claim 1, wherein the acid being removed is HF and the first scrubbing solution comprises a weak solution of HF. 6. The method of claim 1, wherein the first treatment solution comprises H ² SO ⁴ . 7. The method of claim 1, wherein in step (c) the reaction products from step (b) are treated in a second absorber with a second scrubber solution to remove additional amounts of acid. 8. The method of claim 7, wherein the second purifying solution comprises water. 9. The method of claim 7, wherein the second purifying solution comprises H ² SO ⁴ .